minor #4396 Corrected latin abbreviation (GeertDD)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4396).

Discussion
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Corrected latin abbreviation

i.e. = *id est*, “that is”
e.g. = *exempli gratia*, “for example”

Commits
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be86ab6 Yay for latin abbreviations

book/service_container.rst

@@ -251,7 +251,7 @@ looks up the value of each parameter and uses it in the service definition.
 .. note::
 
     If you want to use a string that starts with an ``@`` sign as a parameter
-    value (i.e. a very safe mailer password) in a YAML file, you need to escape
+    value (e.g. a very safe mailer password) in a YAML file, you need to escape
     it by adding another ``@`` sign (this only applies to the YAML format):
 
     .. code-block:: yaml